Gasoline refining



Unite States 2,707,700 Patented May 3, 1955 GASOLINE REFENING Percival C. Keith, Peapack, N. 1., assignor to Hydrocarbon Research, Inc., New York, N. Y., a corporation of New Jersey N Drawing. Application February 19, 1952, Seriai No. 272,495

9 Claims. ((31. 196-36) This invention relates to the treatment of hydrocarbon oils and is more particularly concerned with the treatment of a raw cracked gasoline fraction. The invention is concerned primarily with the treatment of raw cracked gasoline fractions to produce a finish-ed gasoline of commer cially acceptable storage stability and octane number.

At the present time, specifications for commercially acceptable motor gasoline require that it pass an existent gum test, in accordance with ASTM method D381, in which the gasoline must show less than mg. of gum per 100 ml. In addition, it is highly desirable that commercial motor gasoline meet the storage stability requirements set forth in ASTM method D9l048T or D52549. Finally, the demands of modern high compression engines make necessary the production of motor gasoline possessing a high octane rating, usually determined as clear research octane number in accordance with ASTM method D90848T. Arithmetic averages in January 1952, for motor gasoline sold in U. S. cities indicate research octane ratings of 83.2 and 90.0 for regular and premium gasolines, respectively, with such gasolines containing an average of 1.35 and 1.75 cc./gal.,-

respectively, of tetraethyl lead.

In modern petroleum refining practice, it is highly advantageous to convert part or all of the higher boiling fractions of the crude oil to materials boiling in the gasoline range. This is effected by processes which involve the cracking of the higher boiling hydrocarbons into hydrocarbons boiling in the gasoline range. However, in many cases, the gasoline fraction which is produced by cracking (hereinafter referred to as raw gasoline) requires further processing to provide a commercially acceptable product having an existent gum content, storage stability and octane number within the above specified limits. When such raw gasoline does not meet requirements for gum content or storage stability, it is usually found that the gasoline contains over 1% by volume of diolefins and often over 5% by volume of such constituents. Furthermore, it is generally known that such constituents, e. g., acylic and cyclic diolefins, are mainly responsible for high gum content and/or poor storage stability (Sachanen, Conversion of Petroleum, 2nd edition, 1948, Rheinhold Publishing Corp, page 498), although certain nitrogen and oxygen compounds are similarly unstable.

Various processes have been proposed for treating such raw gasoline fractions to bring them within the desired specification limits, and some of these processes have been commercially used with varying effectiveness. However, cracked raw gasolines are generally of moderate to high octane number, containing 10 to 50% by volume of aromatic hydrocarbons and at least 29% by volume of olefins, and known methods for removing gum-forming constituents and improving the storage stability bring about the destruction or conversion of some of these unsaturated compounds. In treatment with sulfuric acid at 0 to 200 F., or over clay at 400 to 700 F., for example, copolymerization of aromatic, monoolefins and diolefins is effected, resulting in a finished gasoline of markedly lower clear research octane number with the yield of finished gasoline approximating by volume for a raw gasoline containing 5 to 10% by volume of diolefins.

Thus it 'is preferable to hydrogenate raw gasolines containing diolefins, so that diolefins are converted to monoolefins, i. e.:

and

RCH2CHz--CH=CHZ The mono-olefin products are of approximately the same clear research octane number as the diolefins, and are of approximately the same boiling point range, so that if such hydrogenation is effected, losses of octane numher and of yield due to polymerization are substantially avoided. However, when hydrogenation at relatively high pressures and relatively low temperatures is employed, the olefins present in the cracked gasoline are completely hydrogenated to parafiins, i. e.

It is well known that such paraffins have clear research octane numbers which are as much as 40 octane numbers lower than the corresponding olefins from which they were formed. Thus, such treatment of a raw cracked gasoline fraction produces a finished gasoline which is generally of appreciably lower clear research octane number than the raw gasoline, and which is in all cases of lower clear research octane number than would have been obtained if the olefins had not been hydrogenated. Where the cracking operation produces a raw gasoline which satisfies octane number requirements without the addition of tetraethyl lead, e. g., above 83 clear research octane number, such utilization of conventional hydrogenation treatment to remove gum-forming constituents re sults in a finished gasoline which is of considerably reduced clear octane number and which consequently requires significant quantities of anti-knock additives to achieve octane requirements. Thus, the principal problem which these cracked raw gasoline fractions of high octane number and of unsatisfactory existent gum content and storage stability present is that of lowering existent gum and increasing storage stability to commercially acceptable limits, while maintaining a high yield of finished gasoline and avoiding any substantial impairment of the clear research octane number. This is a problem which has not been solved in a satisfactory and efiicient manner by prior processes for treating raw gasoline.

A principal object of the present invention is to provide a process for treating raw gasoline fractions containing at least 20% by volume of olefins and of unsatisfactory existent gum content and storage stability, which process will eliminate a substantial portion of the undesired gum-forming constituents, while maintaining the major portion of said olefins.

It is a further important object to provide a process for treating said raw gasoline fractions, which will eliminate a substantial portion of the gum-forming constituents and impart a satisfactory storage stability, while increasing or at least maintaining the clear research octane ratings of said raw gasolines.

It is another object of the invention to provide a process of the character indicated in which high yields of finished gasoline are obtained.

It is another object to provide an improved cracked raw gasoline treating process which avoids the shortcomings of treating processes heretofore proposed.

It is a feature of the invention that cracked raw gasoline is treated in the presence of a material having catalytic activity at elevated temperatures and at a predetermined hydrogen partial pressure such that the bodies which render the gasoline unstable are converted to more stable forms, without significantly decreasing the clear research octane number of the raw cracked gasoline, even when the octane number exceeds 80. In many cases, the process of this invention increased the octane number. Thus, the application of the process to raw gasoline of clear research octane number exceeding 80 makes it possible to meet commercial octane requirements without the addition or" anti-knock agents. Furthermore, in accordance with the invention, finished gasoline yields of more than 90% by volume are obtained even when the raw gasoline contains a large percentage of diolefins, e. g., 5% by volume or more.

In accordance with the invention, a cracked raw gasoline fraction of unsatisfactory storage stability, i. e., failing to meet the commercial existent gum and storage st..- bility requirements in accordance with ASTM methods D381 and D9l04ST or D52549, and containing at least by volume of olefins, is introduced, together with hydrogen, into a treating Zone maintained at a temperature of 800 to 925 F., preferably at a temperature of about 825 to 900 F, in contact with particulate material of the character hereinbelow described. The total pressure in the treating zone and the introduction of hydrogen and raw gasoline are controlled in known manner to provide a hydrogen partial pressure of 50 to 325 p. s. i. (pounds per square inch), preferably 100 to 250 p. s. i. Th total pressure of the system may vary over a relatively wide range, but it is generally preferred to use a total pressure not exceeding about 1000 p. s. i. g. (pounds per square inch gage).

Bauxite is a well known, native aluminum oxide in bydrated form, often containing iron. In commercial practice, the bauxite is ground to the desired particle size and dehydrated by heat treatment, the bauxite then being said to be activated. This heat treatment is carried out at temperatures within a wide range, generally 600 to 1400" F. Activation of bauxite sometimes includes one r tore additional processing steps like acid washing, and mechanical or magnetic separation of admixed minerals. While activated bauxite is a preferred contact material for the process of this invention, it is possible to charge ordinary bauxite into the reaction zone because at reaction temperatures of 900 to 1025 F., and at even higher regeneration temperatures, the bauxite will undergo dehydration and, thus, become activated.

The particulate contact material employed in the treating zone is an alumina of high surface area, viz. a surface area of at least 100 square meters per gram, preferably at least 125 square meters per gram, as measured by low-temperature nitrogen adsorption. The alumina of high surface area employed in accordance with this invention comprises bauxite, activated alumina, and similar preparations of high surface area derived from alumina gels.

Activated alumina is a commercial product well known in the petroleum treating art and is described for example, in Chemical Engineers Handbook (John H. Perry, ed.), third edition (1950), page 905. Alumina gels prepared by precipitation oi aluminum hydroxide from an aqueous solution of a soluble salt such as the nitrate, followed by filtration, washing, drying and calcining oi the precipitate by conventional procedures are also suitable contact materials for the process of this invention.

While substantially pure hydrogen is advantageously used in the process, a gas mixture containing hydrogen and inert gases, such as nitrogen or methane, may be employed with eiiicacy. in the latter case it is preferable to use a gas mixture having at least about by volume of hydrogen in order to avoid the necessity of passing excessively inrge amounts or gas through the reaction zone to provide the desired hydrogen partial pressure of to 325 p. s. i. and in order to avoid the necessity of raising the total pressure of the system to a high value.

The term gasoline fraction as herein used has its conventional meaning, viz., a hydrocarbon fraction boiling within the temperature range of 90 to 400 F., although it will be apparent that the treating process of this invention is applicable to hydrocarbon fractions in which material boiling within the gasoline range comprises the predominant portion of the fraction.

Cracked raw gasoline fractions from various sources are advantageously treated in accordance with the process of the invention but the improved process is of particular value, as already mentioned, in reducing the content of gum-forming constituents and increasing the storage stability of cracked raw gasoline fractions of relatively high octane number, e. g., clear research octane numbers of at least about 80, and more particularly between and 90, containing substantial quantities of monoolefins, such as gasoline fractions produced by the process described and claimed in the copending application of Percival C. Keith, Serial No. 139,758, filed January 20, 1950, now Patent No. 2,606,862. As previously mentioned, the pres out process is effective to remove even large proportions of gum-forming constituents without any appreciable adverse etfect upon the high octane number of the raw gasoline. in some cases the octane number is essentially unaffected, i. e., it is not changed by more than one or two units, whereas in other cases it is even increased by a substantial extent.

In the process described in the above-mentioned Keith application, a crude hydrocarbon oil, particularly a heavy residual product, is cracked at a temperature of 800 to 1050 F. and at a total pressure of 200 to 800 p. s. i. g. in the presence of a particulate contact material and the regeneration product gases produced by treating spent contact material contaminated with carbonaceous material at a temperature of about 1600 to 2500 F. with steam and oxygen of at least by volume purity. The hydrocarbon effluent from that process is fractionated to yieid a cracked raw gasoline which may suitably be treated by the process of this invention.

The invention is, however, not limited to cracked raw gasoline fractions produced in any particular manner but is applicable to any cracked raw gasoline having at least 20% by volume of olefins, and thus a clear research ctane number greater than that of a virgin naphtha, e. g., above about 40. The present process is of particular effectiveness, however, on those cracked raw gasoline fractions having an exceptionally high olefin content, e. g., of the order of 30% by volume higher, and high clear research octane numbers of the order of 80 to 90.

A typical raw gasoline produced by the process of the above-mentioned Keith application has a relatively high octane number, e. g., a clear research octane number of about 90, and contains a high proportion of olefins. Such a raw gasoline generally has, however, a substantial amount of diolefins which tend to render the gasoline unstable as by depositing gums on standing. Cracked raw gasoline fractions to which the present process is of particular application, such as gasoline produced in accordance with the above-mentioned Keith procedure, will generally have the following approximate composition (per cent by volume):

020% paraffins and naphthenes 2540% aromatics 210% diolefins Without tying the invention to any particular theory of operation, the process appears to involve the following types of reactions which take place more or less simultaneously. Diolefins are substantially converted to monoolefins. At the same time, aromatic hydrocarbons are not afiected and only mild hydrogenation of mono-olefins takes place so that the excellent anti-knock properties of the raw gasoline are not impaired. In addition, de-

hydrogenation of naphthenes is facilitated by the conditions employed, resulting in the formation of additional quantities of aromatic compounds of excellent antiknock characteristics.

The raw gasoline treating process is suitably carried out in conventional gasoline treating apparatus wherein, in accordance with the invention, the raw gasoline is introduced into a reaction zone in contact with the catalyst. The apparatus shown in the above-mentioned Keith application may be employed, but preferably the process is carried out in a fluidized bed such as is used commercially in the catalytic cracking of hydrocarbon oils, the hydrogen or hydrogen-containing gas being advantageously employed as the fluidizing medium. The contact material is continuously or intermittently withdrawn from the treating zone and regenerated in any convenient manner, as by treating it at elevated temperature with oxygen or air and, if desired, other gaseous materials such as steam.

The particular apparatus used for the process and the particular method of regenerating the catalyst form no part of the present invention and any convenient apparatus and method of catalyst regeneration may be employed. In regenerating the catalyst care must be taken, however, in accordance with commercial regeneration techniques, to avoid the use of temperatures which destroy or adversely affect the catalyst. In the regeneration of the catalyst of the present process, temperatures in excess of 1400 F. are generally to be avoided.

In order to facilitate the maintenance of the desired temperature in the reaction zone, the raw cracked gaso line to be treated is advantageously preheated to a temperature of 400 to 800 F., preferably about 500 to 700 F., before being fed into the reaction zone. At such temperatures the gasoline is at least partially vaporized.

The hydrogen or hydrogen-containing gas may also be preheated to about the same temperature as the gasoline.

Treatment of the cracked raw gasoline in the reaction zone under the specified conditions is carried out to an extent suflicient to reduce the content of gum-forming constituents in the raw gasoline and to improve its stability to the desired degree. Advantageously, the desired reaction is insured by employing a raw gasoline feed rate in the range of 0.5 to 5, preferably 0.5 to 1.5, volumes of liquid per hour per volume of catalyst, while employing a hydrogen flow rate of 500 to 2500 standard cubic feet (calculated as pure hydrogen) per barrel of raw gasoline fed.

The effluent from the treating zone will contain vapors of the hydrocarbons within the gasoline range admixed with a small amount of higher boiling hydrocarbons and more volatile compounds. The efiluent is fractionally distilled to separate the desired gasoline fraction from the other constituents. The finished gasoline fraction thus produced is of high stability and high octane number and meets the specifications for commercial motor gasoline notwithstanding the presence of a substantial quantity of diolefins originally in the cracked raw gasoline,

For a further understanding of the invention, reference is made to the following specific examples which are intended as illustrative of the process without, however, being intended as lirnitative thereof.

In the following examples the cracked raw gasolines which are treated were obtained from heavy residua from East Texas and West Texas-New Mexico crude oils were subjected to cracking in accordance with the aforesaid Keith process at a temperature of about 900 F. in the presence of the regeneration gases resulting from the decomposition of the carbonaceous residue on the particulate carrier with steam and oxygen of 95% by volume purity at a temperature of about 1700 F. In each case, the efiiuent from the cracking operation was condensed and fractionally distilled to separate the raw gasoline fraction which was treated.

4ST) 90.8 Bromine number cgs./gm. (ASTM-D87546) 60 Olefin content, volume percent 41 Copper dish gum, mg./ ml. (ASTM-D9l0- Stability, minutes (ASTM-D525-49) This raw gasoline is heated, for example, by passing it through the coils of a tube still, to a temperature of about 700 F. The gasoline is then discharged into a reaction zone containing fluidized particles of activated bauxite. The gaseous treating atmosphere is provided and the fluidization of the bauxite particles is simultaneously effected by introducing a stream of hydrogencontaining gas into the bottom of the reaction zone. The gas contains 40 mol. percent hydrogen, the remainder being inert gas. A portion of the fluidized catalyst is continuously removed from the reaction zone and passed to a regenerator, and a corresponding amount of regenerated catalyst is continuously returned to the reaction zone. In the reaction zone, the temperature is maintained at 890 F. and the total pressure is maintained at 400 p. s. i. g. The heated raw gasoline is introduced into the reaction zone at a rate to provide a space velocity of 1.0 volume of liquid gasoline per hour per volume of catalyst in the reaction zone and the hydrogen is introduced at a rate to provided a hydrogen partial pressure of 152 p. s. i.

The gasiform effluent is continuously removed from the top of the reaction zone, condensed, and then subjected to fractional distillation to separate from the gasoline more volatile hydrocarbons and gases, particles of the catalyst which may have been carried over with the eflluent, and a small proportion of higher boiling hydrocarbons formed in the reaction zone. Analysis of the recovered gasoline fraction shows it to have the following characteristics:

Octane number, CFRR clear (ASTM- D90848T) 91.3. Bromine number, cg./ gm. (ASTM- D875-46) 78. Olefin content, volume percent 53. Copper dish gum, mgs./ 100 ml.

(ASTM-D9 l O-4ST) Stability, minutes (ASTM-D525- 49) More than 1100. Existent gum, mg./ 100 ml. (ASTM- D-381-49) Less than 5.

The yield of gasoline is 94.1% by volume of charge, and the total yield of liquid products is 98.0% by volume of charge.

It will be seen from the foregoing example that, in accordance with the process therein described, a cracked raw gasoline having a high content of gum forming constituents, as indicated by the 400 mgs. obtained in the copper dish gum test and the 145 minutes break down in the stability test, is converted to a finshed gasoline containing a substantial quantity of olefins, and having stability and gum-forming characteristics meeting commercial requirements. In the foregoing example, these significant improvements in the gasoline have. been elfected with an increase in octane number of one-half unit. The yield of this high quality finished gasoline is excellent.

Example 11 This example shows the application of the process of the invention to a cracked raw gasoline obtained in accordance with the procedure described hereinabove from I a West Texas-New Mexico residuum. This cracked raw gasoline had the following characteristics:

Octane number, CFRR clear (ASTl\dD908-48T) 87 Bromine number, cg./gm. (ASTM-D875-46) 74 Olefin content, volume percent 51 Copper dish gum, Ings./1OO ml. (ASTM-D9l0- 48T) 400 Stability, minutes (ASTM-D525-49) 115 Following the process described in Example I, the above-identified cracked raw gasoline is treated in a reaction zone maintained at a temperature of 870 F. and at a total pressure of 400 p. s. i. g., by introducing the preheated raw gasoline at a rate to provide a space velocity of 0.9 volume of liquid per hour per volume of the catalyst in the reaction zone, while maintaining a hydrogen partial pressure of 170 p. s. i., employing a hydrogen-containing gas comprising 50 mol percent of hydrogen admixed with inert gas.

The treated gasoline fraction, recovered as described in Example I, has the following characteristics:

Octane number, CFRR clear (ASTMD908- 48T) 86.4 Bromine number, cg./gm. (ASTMD87546) 75 Olefin content, volume percent 51 Copper dish gum, mg./1OG ml. (ASTM-D910- 4ST) 4 Stability, minutes (ASTMD52549) 1200 Existent gum, mg./l00 ml. (ASTM-D38l-49L- 2 The yield of gasoline is 90.9% by volume of charge, and the total yield of liquid products is 95.6% by volume of charge.

In this example there is produced a high yield of finished gasoline of excellent stability and falling Well within the commercial limits with respect to gum formation and substantially without change in olefin content or clear research octane number.

In view of the various modifications of the invention which will occur to those skilled in the art upon consideration of the foregoing disclosure without departing from the spirit or scope thereof, only such limitations should be imposed as are indicated by the appended claims.

What is claimed is:

l. A method of eliminating gum-forming constituents from a highly olefinic hydrocarbon fraction, which comprises bringing hydrogen and a hydrocarbon fraction containing gum-forming constituents and more than by volume of olefins imparting to said hydrocarbon fraction a high octane number into contact with an alumina of high surface area and free of added catalysts and promoters in a reaction zone maintained at a temperature in the range of 800 to 925 F., the contact of said hydrogen and said hydrocarbon fraction resulting in a net consumption of hydrogen, passing said hydrocarbon fraction through the reaction zone at a space velocity in the range of about 0.5 to 5 liquid volumes per hour per volume of said alumina, maintaining the partial pressure of hydrogen in said reaction zone in the range of 50 to 325 p. s. i., and recovering from the resulting reaction eflluent a highly olefinic hydrocarbon fraction with a substantially decreased content of gum-forming constituents and containing a major portion of said olefins and having a high octane number.

2. A method of eliminating gum-forming constituents from a highly olefinic hydrocarbon fraction, which comprises bringing hydrogen and a hydrocarbon fraction containing gum-forming constituents and more than by volume of olefins imparting to said hydrocarbon fraction a high octane number into contact with an alumina of high surface area and free of added catalysts and promoters in a reaction zone maintained at a temperature in the range of 825 to 900 F, the contact of said hydrogen and said hydrocarbon fraction resulting in a net consumption of hydrogen, passing said hydroall carbon fraction through the reaction zone at a space velocity in the range of about 0.5 to 5 liquid volumes per hour per volume of said alumina, maintaining the partial pressure of hydrogen in said reaction Zone in the range of. to 325 p. s. i., and recovering from the resulting reaction efiluent a highly olefinic hydrocarbon fraction with a substantially decreased content of gum-forming constituents and containing a major portion of said olefins and having a high octane number.

3. A method of eliminating gum-forming constituents from a highly olefinic gasoline fraction, which comprises bringing hydrogen and a gasoline fraction containing more than 2% by volume of diolefins and more than 30% by volume of olefins and having a clear research octane number or at least about into contact with an alumina of high surface area and free of added catalysts and promoters in reaction zone maintained at a temperature in the range of 825 to 900 F, the contact of said hydrogen and said gasoline fraction resulting in a net consumption of hydrogen, passing said gasoline fraction through the reaction zone at a space velocity in the range of about 25 to 5 liquid volumes per hour per volume of said alumin" maintaining the partial pressure of hydrogen in said action zone in the range of 50 to 325 p. s. i., and recovering from the resulting reaction efiluent a highly oiefinic gasoline fraction with a substantially decreased ccntent of said diolefins and containing a major portion of said olefins and having a clear research octane number of at least about 80.

4. A m according to c aim 3 wherein the alumina is activated bauxite and the hydrogen partial pressure is in the of l'QO to 250 p. s. i.

5, A method of eliminating gum-forming constituents from a highly olcfinic gasoline fraction, which cornprises bringing hydrogen and a gasoline fraction containing gum-forming constituents and more than 20% by volume of olefins imparting to said gasoline fraction 21 high octane number into contact with an alumina of high surface area free of added catalysts and promoters in a reaction zone n'iaintaincd at a temperature in the range of 890 to 925 F, the contact of said hydrogen and said gasoline fraction resulting in a net consumption of hydrogen, passing said gasoline fraction through the reaction zone at a space velocity in the range of about 0.5 to 5 liquid volumes per hour per volume of said alumina, maintaining the partial pressure of hydrogen in said reaction zone in the range of 100 to 250 p. s. i., and recovering from the resulting reaction effluent a highly olcfinic gasoline fraction with a substantially decreased content of gum-forming constituents and containing a major portion or" said olefins and having a high octane number.

6. A method of eliminating gum-forming constituents from a highly olcfinic gasoline fraction, which comprises bringing hydrogen and a gasoline fraction containing gum-forming constituents and more than 20% by volume of olefins and having a clear research octane number of at least about 80 into contact with an alumina of high surface area and free of added catalysts and promoters in a reaction zone maintained at a temperature in the range of 825 to -1) F, the contact of said hydrogen and said gasoline fraction resulting in a net consumption of hydrogen, passing said gasoline fraction through the reaction zone at a velocity in the range of about 0.5 to 5 liouid volumes per hour per volume of said alumina, maintaining the partial pressure of hydrogen in said rcac"c'i zone in the range of 50 to 325 p. s. i., and recovering from the resulting reaction efiluent a highly olcfinic gasoline fraction with a substantially de creased content of gum-forming constituents and containing major portion of said olefins and having a clear research octane number of at least about 80.

7. A method according to claim 6 wherein the gasoline frnctioz passes through the reaction zone at a space velocity of 0.5 to 1.5 liquid volumes per hour per volume of said alumina.

8. A method of eliminating gum-forming constituents from a highly olefinic raw gasoline, which comprises bringing hydrogen and a raw gasoline containing a troublesome quantity of diolefins and more than 20% by volume of olefins, said raw gasoline having a clear research octane number of at least about 80, into contact with activated alumina free of added catalysts and promoters in a reaction zone maintained at a temperature in the range of 800 to 925? F., the contact of said hydrogen and said raw gasoline resulting in a not consumption of hydrogen, passing said raw gasoline through the reaction zone at a space velocity in the range of about 0.5 to 5 liquid volumes per hour per volume of said alumina, maintaining the partial pressure of hydrogen in said reaction zone in the range of 100 to 250 p. s. i., and recovering from the resulting reaction eifiuent a highly olefinic finished gasoline substantially free of said diolefins and containing at least 20% by volume of said olefins and having a clear research octane number over 80.

9. A method according to claim 8 wherein the raw gasoline passes through the reaction zone at a space velocity of 0.5 to 1.5 liquid volumes per hour per volume of said alumina.

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1. A METHOD OF ELIMINATING FUM-FORMING CONSITUENTS FROM A HIGH OLIFICE HYDROCARBON FRACTION, WHICH COMPRISES BRINGING HYDROGEN AND A HYDROCARBON FRACTION CONTAINING GUM-FORMING CONSITUTENTS AND MORE THAN 20% BY VOLUME OF OLEFINS IMPARTING TO SAID HYDROCARBON FRACTION A HIGH OCTANE NUMBER INTO CONTACT WITH AN ALIMINA OF HIGH SURFACE AREA AND FREE OF ADDED CATALYSTS AND PROMOTERS IN A REACTION ZONE MAINTAINED AT A TEMPERATURE IN THE RANGE OF 800 TO 925* F., THE CONTACT OF SAID HYDROGEN AND SAID HYDROCARBON, FRACTION RESULTING IN A NET CONSUMPTION OF HYDROGEN, PASSING SAID HYDROCARBON FRACTION THROUGH THE REACTION ZONE AT A SPACE VELOCITY IN THE RANGE OF ABOUT 0.5 TO 6 LIQUID VOLUMES PER HOUR PER VOLUME OF SAID ALUMINA, MAINTAINING THE PARTIAL PRESSURE OF HYDROGEN IN SAID REACTION ZONE IN THE RANGE OF 50 TO 325 P.S.I., AND RECOVERING FROM THE RESULTING REACTION EFFLUENT A HIGHLY OLEFINIC HYDROCARBON FRACTION WITH A SUBSTANTIALLY DECREASED CONTENT OF GUM-FORMING CONSTITUENTS AND CONTAINING A MAJOR PORTION OF SAID OLEFINS AND HAVING A HIGH OCTANE NUMBER. 